Korg - TBN-1 Tonebooster  [schematic]

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Korg - TBN-1 Tonebooster

Postby gigelmargel » 15 Dec 2013, 17:22

Hello all,

I have an old Yamaha Tone Booster TB-1 and it sounds pretty good.

The main problem is the very low efficiency of the tone pots: the bass pot has almost no effect, while the treble pot has a little more one.

The schematic is here:
korg tonebooster.jpg


Anyone has some mods for it?

Thank you very much!
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Re: Anyone knows some mods for Korg/Yamaha Tonebooster?

Postby gigelmargel » 22 Dec 2013, 08:46

No ideea?
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Re: Anyone knows some mods for Korg/Yamaha Tonebooster?

Postby dai h. » 22 Dec 2013, 13:45

(I'm assuming this something a couple of decades old) have you tried fresh aluminum electrolytics? They can age and lower in value which would lessen bass(my understanding is this is to do with evaporation of the liquid inside--not sure if wholly or partly due to). Specifically the power supply ones (100uF,10uF), the gain cap(1uF), output coupling (10uF).
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Re: Anyone knows some mods for Korg/Yamaha Tonebooster?

Postby gigelmargel » 30 Dec 2013, 08:36

dai h. wrote:(I'm assuming this something a couple of decades old) have you tried fresh aluminum electrolytics? They can age and lower in value which would lessen bass(my understanding is this is to do with evaporation of the liquid inside--not sure if wholly or partly due to). Specifically the power supply ones (100uF,10uF), the gain cap(1uF), output coupling (10uF).

Thx dai! I will try to change all the caps, but other people seems to have the same problem.
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Re: Anyone knows some mods for Korg/Yamaha Tonebooster?

Postby dai h. » 30 Dec 2013, 20:18

well if you need more sophisticated suggestions (unfortunately) I'm not knowledgable enough to give you much more than my suggestion to change to new caps, but FWIW in this demo of the Korg version of the same pedal:


Link


I am hearing (through my so-so PC speakers) an increase and decrease in bass. Have you tried new caps yet?

From what I see, the tone control section looks very much like that found in many guitar amps (which AFAIK only reduce from a maximum point of least loss--if that makes sense), and the op amp after gives a bit of gain (about a 5:1 ratio of the feedback resistors). Perhaps a tone circuit that adds gain is more suitable? Maybe an EQ pedal (to give more control instead of what sounds like a general bass boost)?
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Re: Korg - TBN-1 Tonebooster  [schematic]

Postby modman » 13 Jan 2018, 21:58

Service manual
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